Stationary waves emerge in systems in which the collective mode spectrum is different
from the linear one. The well-known example is ship waves on a
water surface
(see, for instance, [1]}). The theory of ship waves was developed by Kelvin.
The interest in
stationary waves was renewed recently in connection with the study of the superfluidity
of atomic Bose-Einstein condensates (BECs). Stationary waves in \(^{87}\) Rb BEC were
observed in [2]} (see also ).
